mirror of
https://github.com/torvalds/linux.git
synced 2025-04-09 12:44:25 +00:00
d9d2a68ed4
Landlock IDs can be generated to uniquely identify Landlock objects. For now, only Landlock domains get an ID at creation time. These IDs map to immutable domain hierarchies. Landlock IDs have important properties: - They are unique during the lifetime of the running system thanks to the 64-bit values: at worse, 2^60 - 2*2^32 useful IDs. - They are always greater than 2^32 and must then be stored in 64-bit integer types. - The initial ID (at boot time) is randomly picked between 2^32 and 2^33, which limits collisions in logs across different boots. - IDs are sequential, which enables users to order them. - IDs may not be consecutive but increase with a random 2^4 step, which limits side channels. Such IDs can be exposed to unprivileged processes, even if it is not the case with this audit patch series. The domain IDs will be useful for user space to identify sandboxes and get their properties. These Landlock IDs are more secure that other absolute kernel IDs such as pipe's inodes which rely on a shared global counter. For checkpoint/restore features (i.e. CRIU), we could easily implement a privileged interface (e.g. sysfs) to set the next ID counter. IDR/IDA are not used because we only need a bijection from Landlock objects to Landlock IDs, and we must not recycle IDs. This enables us to identify all Landlock objects during the lifetime of the system (e.g. in logs), but not to access an object from an ID nor know if an ID is assigned. Using a counter is simpler, it scales (i.e. avoids growing memory footprint), and it does not require locking. We'll use proper file descriptors (with IDs used as inode numbers) to access Landlock objects. Cc: Günther Noack <gnoack@google.com> Cc: Paul Moore <paul@paul-moore.com> Link: https://lore.kernel.org/r/20250320190717.2287696-3-mic@digikod.net Signed-off-by: Mickaël Salaün <mic@digikod.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.